Plasma and Fusion Research

Volume 17, 2401095 (2022)

Regular Articles

Vibrational Temperature Estimation of Nitrogen Molecules in Radio-Frequency (RF) Produced Plasma

Nandini YADAVA^1,2), Sachin S. CHOUHAN³⁾, Amulya SANYASI⁴⁾, Uttam SHARMA³⁾, Jayashree SHARMA³⁾, Malay B. CHOWDHURI⁴⁾, Joydeep GHOSH⁴⁾ and Ankur PANDYA⁵⁾

1): Institute of Science, Nirma University, Ahmedabad 382 481, Gujarat, India
2): Department of Aerospace Engineering, Indian Institute of Technology Kanpur, Kanpur 208 016, Uttar Pradesh, India
3): Shri Vaishnav Vidhyapeeth Vishwavidyalaya, Sanwer Road, Indore 453 111, India
4): Institute for Plasma Research, Bhat, Gandhinagar 382 428, India
5): Institute of Technology, Nirma University, Ahmedabad 382 481, Gujarat, India

(Received 10 January 2022 / Accepted 29 June 2022 / Published 24 August 2022)

Abstract

A capacitive coupled radio frequency (RF) plasma system has been developed for producing tungsten coated graphite tiles using plasma assisted chemical vapor deposition (PACVD) technique. To characterize the deposition chamber for optimal plasma parameters, small amount of air is released into the hydrogen plasma purposefully to measure its gas temperature using spectral bands of nitrogen molecule. Optical emission spectra in the wavelength range 350 to 900 nm have been recorded with a miniature spectrometer. Molecular spectral bands of N₂ (B³Π_g−A³Σ_u⁺) have been observed and identified as three bands from the nitrogen 1PS (Δν = 2, 3 & 4). These bands are simulated using MATLAB code developed in-house by considering Boltzmann distribution of particles in the vibrational states. The experimental spectra have been modelled with the simulated spectrum through the best-fit technique by iterating the latter one with different temperature values. Boltzmann plot method is also utilized to evaluate plasma gas temperature using identified vibrational bands. The estimated temperature using spectral modelling method matches fairly well with Boltzmann plot method. The estimated vibrational temperatures are in the range of ∼7000 - 8000 K, an order higher than the room temperature ∼300 K.

Keywords

rovibrational spectroscopy, OES, tungsten coating, RF plasma, PACVD, vibrational temperature, nitrogen 1PS, hydrogen Fulcher band

DOI: 10.1585/pfr.17.2401095

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References

[1] M.A. Lieberman and A.J. Lichtenberg, Principles of plasma discharges and materials processing (John Wiley & Sons, 2005).
[2] V. Philipps et al., Phys. Scr. T145, 52 (2011).
[3] S. Mathur and P. Kuhn, Surf. Coat. Technol. 201, 806 (2006).
[4] S.-H. Hong et al., Fusion Sci. Technol. 68, 36 (2015).
[5] R.L. Tanna et al., Nucl. Fusion 57, 102008 (2017).
[6] S.S. Chauhan et al., Mater. Res. Express 5, 115020 (2018).
[7] U. Sharma et al., J. Phys. Conf. Ser. 755, 012010 (2016).
[8] H.-J. Kunze, Introduction to plasma spectroscopy, vol.56 (Springer Science & Business Media, 2009).
[9] K.-P. Huber, Molecular spectra and molecular structure: IV, Constants of diatomic molecules (Springer Science & Business Media, 2013).
[10] R.S. Mulliken et al., RMP 4, 1 (1932).
[11] G. Herzberg, Molecular Spectra and molecular structure-Vol I (Read Books Ltd, 2013).
[12] H. Nassar et al., J. Phys. D: Appl. Phys. 37, 1904 (2004).
[13] F. Roux and F. Michaud, Can. J. Phys. 68, 1257 (1990).
[14] F.R. Gilmore et al., J. Phys. Chem. Ref. Data 21, 1005 (1992).
[15] Y.-C. Kim et al., Phys. Plasmas 22, 083512 (2015).
[16] D.R. Farley et al., J Quant Spectrosc. Radiat. Transf. 112, 800 (2011).